Station for duplex wireless telegraphy



May 25 1926.

H. J. J. M. DE R. DE BELLESCIZE STATION FOR DUPLEX WIRELESS TEIJGRPHY Ljmlllll* Filed August 18a 1.919

Patented May 25, 1926.

unirse stares rrENT oFFIcE.

STATION FOR DUPLEX VVIREXESSi'1ELEGrRAIEHY.`

Application filed August 18, 1919. Serial No. 318,368.

Wireless stations equipped for duplex working7 that is to say, for simultaneous transmission and reception of messages, comprise each a separate transmitting appa- 'l ratus and areceiving apparatus, these two apparatuses being connected together by a line t telegrapliic, telephonic or service lines) serving to carry on the service.

The difiiculty in the working of such stations is due to the disturbing eitect ot the transn'iitting apparatus upon thereceiving apparatus ot the same station which is still intended to continue to listen during the transmission.

55 It has been proposed hitherto to remedy this ditiiculty by the separate or combined use of various methods hereinafter referred to, which are however attended by the following drawbacks 1; A rather considerable distance is necessary between the transmitting and receiving apparatuses ot the same station (it `has not been possible hitherto to obtain good results with a distance under kilometres in the i case of stations for transatlantic communications). This distance is a drawback to the facility of the operation of the station.

2. For the two stations working in duplex very different transmission wave lengths (at least 10%) must be chosen.

lt is to be noted that the adoption of the same wave length or of very nearly equal wave lengths for the two simultaneous transmissions would have two important advantag s, namely: (l) the interference occasioned at ,other wireless receiving stations tuned to a different wave length would be diminished, and (2) the other stations would be prevented trom intercepting at least one (if not both) of the series of signals exchanged on the same wave. This interception vwill be more particularly prevented in the case ot stations which do not have closely selec v tive receiving capabilities, and to stations 1'" situated in proximity to the plane of the two cooperating duplex stations. This latter advantage is important in time of war in order tov prevent the interception by the enemy stations.

With the use at each ot the two stations equipped Jfor duplex working, of a other station with which communication is to be established, it has been found that the open or closed aerials employed hitherto are very imperfectly constructed and directed for this purpose, and that there is no direction in which their radiation or their own sensitiveness can be considered as being practically nil.

(4) it is also known to utilize a small open compensating aerial directed horizontally at right angles tothe bearing of the distant transmitting station, and consequently at right angles to the receiving aerial to which it is inductively coupled by means of a coil.

. It is to be noted also that duplex receiving over long distances has been done alreadyY on an open aerial.

The present invention consists in improvements in wireless stations for duplex working designed to do away with the drawbacks of the devices hereinbefore referred to.

In order to cancel the disturbing effect of the transmitting apparatus upon the receiving apparatus of one and the same station, one or the other of the following conditions or their combination must be established according to the present invention.

In the accompanying drawing, wherein a practical embodiment of the invention is illustrated,

Figure l shows the assembled apparatus diagrammatically, Epindicating the emitter or sending station`r B the receiver D and D2 a compensating device.

Fig. 2 is a detail of the receiver element.

Fig. 3 is a view indicating the manner in which the 'receiver element may itself be used as a compensating element.

l. The receiver antenna is formed ot a closed trame, rotatable about a vertical-axis, and mounted'as indicated in Fig. 2. It comprises a principal seit induction L1 and L2 directly actuated by the Hertzian waves, a tuning condenser C and inductively excites a secondary L C which, like the remainder et thel receiver is enclosed in a Faraday cage Y O. The coupling self induction forming part of the primary circuit is formed by t\vo identical coils a, similarly coupled With the secondary self induction coil L', and Wound in such manner that their inductive effects due to the current circulating about the frame, are added with respect to the secondary. rlhe central point N of the conductor connecting the coils a, 't is connected to the Faraday cage O, so that Athe primary circuit is thus formed of two halves L1 and a and L2 and b, electrical-ly -identical and lsymmetrical with respect to the condenser C and With the ground Nl.

The object sought by this arrangement is as follows: First, the secondary L L C and theentire receiver actuated by this secondary is shielded by the Faraday cage O from the direct infiuence of the adjacent sending station (Fig. l), so that the noise of this station cannot be transmitted .except through therotating frame L, L2.

This accomplished, the frame should be considered from a double viewpoint.

The closed normal circuit (i L2 C L1 is first distinguished; the magnetic flux due to the emission from the station E and engaged by this circuit creates there yan clcctron'iotive force and a current I which acts inductively on the secondary. In the present application it issought to direct the frame so as to render the lengaged. flux, and hence the disturbing current l, minimum.

l't is to be further noted that a true open antenna., formed by the frame and its connections with the ground is necessarily superposed With relation to the closed circuit. ln ordinary mounting this open antenna exerts on the. secondary and the remainder of the receiver an action, generally electrostatic which would be detrimental to the present application. In the balanced mounting of Fig. 3 this action is eliminated, in fact, the variations in potential of the small self indnctions a, connected to `the ground are Weak, and all of the rest of the frame is outside the Faraday cage and there is practically no electrostatic action between the primary and secondary circuits. On the other hand, equal currents i, "il, circulate between the frame and the ground, but by re son of the arrangements described for the coils a and 7), the electromctive force created in the secondary L L by the coil a traversed by the current a immediately nullifies that created by the current il, traversing the coil Zi. The action of the Vopen antenna on the receiver is hence zero.

rihe noise caused by the sending station adjacent is thus reduced to the inductive effect of the normal current I, due to the variation of the flux engaged by the closed frame.

The selective effect of the frame is thus carried to its maximum efficiency; rst, since by directing it so as to reduce the flux engaged it is possible to eliminate or at least to materially reduce the noise, then by elimina ting the disturbing action of the open antenna, usually but slightly deadened, the syntoniif: phenomenaare more marked and permit of the profiting from the discorde existing between the Wave emiited thrinlgh the sending sation E and that of the signal l'or which receiver B is standiiig by for.

The same arrangements may be applied to thc secondary L C as well as to the resonators.

2. The transmitting apparatus must be constructed in such a manner that it will have a synnnetry plane to which the radiated magnetic field will be at right angles; and as a receiver there must be employed a closed and balanced frame Which is to be placed in the vicinity of the symmetry plane and musi be directed at right angles to the latter.

Under these conditions the frame will contain the magnetic Avector of thev field and Will therefore be sheltered from its action.

3. If this symmetry of the transmitting apparatus cannot be completely carried into effect (which is more particularly the case with existing apparatus), then there must be employed as the receiver a balanced frame lthe plane of Which is inclined in such a manner as to contain the vector of the radiated magnetic field, or at least the component of the field vector corresponding to the main Wave.

4. The residual action Which in spite of the foregoing precautions might still remain in the receiving apparatuses, should be cancelled by means of a compensating aerial actuated from a distance by the transmitting apparatus and acting in its turn upon the receiving apparatus; this compensatingl aerial being constructed and placed in such a manner that it Will not change in any Way' the syntonic, directional or other properties of the receiving apparatus.

5. One or more of the residual effects subsisting in the receiving apparatuses must be varied in amount and phase, in such a manner as to render the total sum of these residnal effects equal to nil.

A description is hereinafter given by Wav of example, of a number of apparatus which alloW of fulfilling the above stated conditions, and of a number of schemes of mounting which have appeared to be the best forl attaining the desired result.

The accompanying drawings illustrate these apparatus and these mountings.

I. Arm/agement of n, transmitting appr/,- mtas haci/ag a symmetry plana-The magnetic field produced by a transmitting apparatus is due to the energy that is radiated not only by the aerial but also by all thi conductors actuated by it (standards, supports, adjacent aerial lines, etc.). Further,

the number of Waves that are emitted is generally a multiple (coupling Waves, harmonic Waves, multiple resonance Waves, Waves due to the `fact that anaerial however well constructed it may be, can never be considered as a simple oscillator) ,so that at each point ot the surrounding space the radiated magnetic lield cannot be represented by single vector, but must be represented by a group ot vectors.; each vector revolves in a plane with a. velocity corresponding to the -trequency ot the Wave by which it is produced; these different planes ot' rotation do not generally coincide With one another.

Nevertheless, according to the present invention, a transmitting apparatus may be constructed having a plane ot symmetry, and such that at each point of this plane all the vectors instead of rotating in the planes, oscillate according` to one and the same .fixed direction in space; this direction is at right angles to the symmetry plane of the transmitting apparatus.

For this purpose (Fig. 1) the t 'ansinitting aerial, as likewise all the adjacent conductors actuated by it with a suiiicient intensity (lines, standards), are so constructed that to each one of their ei'ements (aa) there corresponds another element (a a) which is geometrically symmetrical in relation to a plane and', and that the currents passing through (aa) and (a a) are at every instant equal and in the same direction. This result will be obtained by the equalization of the electric and `geometric characteristics ot the two elements (aa, a a). Under these Yconditions the magnetic field at any point ot the symmetry'plane Will be represented by vectors at right angles to said plane irrespective of the frequencyl of the oscillations ot the transmitting aerial. i

It a closed frame B serving as a receivingaerial be placed in the neighbourhood ot the symmetry plane of the transmitting j aerial, and be directed at right angles to said plane, and it further a perfect electric balance of this frame be effected by one of the methods described in my copending U. S. application for patent Serial No. 249,910, tiled in 1918, Patent No. 1,429,572, it will not be capable of transmittingto other receiving apparatuses any action originating from the transmitting apparatus.

Consequently the system illustrated diagrammatically in Fig. 1 Will be adopted for the duplex station. E is the transmitting station; it has a plane of symmetry can which is directed at right angles or approximately at right angles to the direction EE, o'l the distant duplex station El. The balanced receiving trame B is placed in such a manner as to have its centre approximately in the plane ewa and to be directed at right angles to said plane.

II. Inclination. of the receiving aerial when the corresponding transmitting appa ratas has no symmetry plane (general case or" the transmitting apparatuses at presentin use),-In this case, as above stated, the magnetic field at each point can be represented by a group of vectors each rotating in a plane. The vector co 1responding to the main Wave radiated by the transmitting? aerial is naturally by tar the most impor-- tant, and in modern installations the othei` vectors are sufficiently small that the oscillations by Which they arcproduced, Will be eliminated at the receiving station by syntonic adjustment.

The eliect ot the vector due to the main wave which alone is to be considered, Will be annulled by making the plane of the receivinn' trame coincide With the plane ot rotation ot the said vector. This leads generally to inclining the plane of the trame to the vertical by an angle determined by trial.

Under these conditions a Well balanced vreceiving' 'frame Will be practically protected transmitting apparatus. This is a secondV solution oit the problem.

Hl. Annulation of the induced residual electra/notice force by means of an auxiliary compense/,ting circuit-This annulation may be produced in the case Where the receiving' circuit is a trame closed by the device illustrated in Fig. 1.

B is the receiving frame Which is directed and Which is first inclined with all the desired precision in such a manner4 as to reduce to a minimum the inconvenience caused to the listening by the emission ot the adjacent apparatus; this inconvenience being increased for instance by the intensity of the sound in telephonie listening devices. There still remains in many cases a residual disturbing eti'ect that may be considered as being due to the electro-motive force induced by a magnetic component (Xn) oscillating along a line (a) at right angles to the plane oit the trame. It the precautions (balanc ing, etc.) above referred to have been sutciently observed, this component Will be considerably smaller than the component (Y) contained in the plane of the trame and rotating in the said plane. It is proposed according to thepresent invention to utilize liti the action ot the component (Y) tor annul Y pan direct inductive action upon the receiver is absolutely nil. T he plane of (D2) is on the contrary coincident with the plane of the frame B. This coil which is practically sheltered from the radiation of the transmitting apparatus is couple-d inductively to the receiving frame.

ation and practice have shown that there an infinity of ways of choofnne` the number of turns. the surface. the self-induction and the res ,ance of the coils (I), D3), as also the capacity of the circuit in such a manner that the oscillation induced in the compefiai'zinp; circnit (l), De C), and transn'iitted by it to the receiver shall annul exactly the residual electromotive force reniain o' in the latterj'even when the receiver is adgusted to catch a wave tl at is equal to or very closely equal to the wave radiated from the station (E). rIhis l` rst result can only be obtained with a well balanced f me.

It will be understood by reason of the arrangement adopted for the compensating circuit. that surface and the number of turns of the winding' (Il) (hence the action of the emitting` apparatus upon the compensator) can be increased without 'the direct action of the said winding upon the receiving frame which is always nil, being increased in any way. rIhis allows of diminishing as much is desired, the coupling of the winding (D2) with the frame The qualities of the receiver as regar-ds syntony, its directional qualities, and others, will therefore be much less affected by this correcting means than they would be by any of those that are at present in use.

The same effect might be obtained with a single compensating windingwhich would be suitably chosen and directed, replacing the whole (D1, D2) and coupled inductively to the receiving' frame (B), because the effect of two windings can always be produced by a single suitably chosen and directed winding.

IV. Annulation of the residual effects subsz'szng in the receiver, by otctz'rlg upon one or more of tem so as to compensate the @Mers as regards amount mal phase.- As has been shown above, the entire receiver frame must be considered as a closed antenna and open antenna at the same time: this dual state is inevitable.

Up to the present, the applicant has attempted by seperate means to annual the disturbing` oscillation generated in the closed aerial, and to stop the transmission to the detecting devices of the effects due to the disturbing oscillation generated in the open aerial.

But there is another way, and by a suitable regulation of the circuits it can be arranged thatI the disturbing actions of these two aerials upon the detecting' apparatus shall balance one another exactly.

In other words, the open antenna formed by the frame itself should replace the separate compensating circuit l)1 D2 shown on Fig. 2.

This result may be attained by different methods; Fig. 3 shows an example which consists in introducingY a resonator L3 G I, on the conductor connecting the centre N of the frame with the ground.

The operation and manipulation ot this mounting,l is as follows:

The frame being' tuned to the signal. to be received and directed so as to reduce the disturbing actions caused by the adjacent sender E to as great a degree as possible,

the magnetic flux created by the emitter or sending station through the closed circuit Il, B2 C is not generally nullitied at once. The residual current I due to the periodical variation of said flux induces in the secondary L C a certain electroin otiic force. A sin (wail-e) represents the pulsation (9mtimes the frequency) of the emission E: the amplitude A is proportional to the flux engaged; the phase e is lined by the condition that the circuit L, L2 C is coinpnlsorily tuned to the signal to be received.v but the operator may, at will, modify e by turning the frame a half turn.

It is desired to compensate this electromotive force. A sin (w-i-e) by another B sin (wt-Hb) created by the frame acting; as an open aerial; this condition requires that there be obtained simultaneously (l.) w26-P180.

Now, the open aerial is composed of two semi-coils L1 L2 which form a sort of terminal capacity, of the resonator L3 C?, and of the ground; this aerial exerts on the secondary L C an electrostatic action, proportionai on the one hand to the capacities C between the primary and the secondary, and on the other, the tension developed between the. point N and the ground. This action, the pulsation of which is necessarily equal to that fw of the sending station E, can only be represented by the formula B sin (wt-Hb). To balance the inequalities (l) it is necessary only to be able to rerulate separately the amplitude B and the phase 1/1; this is eifectively possible.

On the one hand, the manipulation of the condenser C, permits of imparting to the phase 1]/ a continuous variation capable of attaining' 180; thus to reproduce the value (ed-180), which is itself determined only at 180, the frame is given a half turn. On the other hand the movement of the slide Q acts directly on the potential of the point N, then on the amplitude B: the two inequalities (l) may thus be balanced. Regulation is effected by successive approximations, based on telephoniev indications; the

lll

disturbances ot station E could not be heard.

What I claim is: Y

l. In a'station tor duplex` radio telegraphy, a receiver comprising secondary circuit and a balanced receiver trame coupled thereto, said frame comprising in series a principal self induction capable of beinO' directed and serving as a closed aerial, a tuned condenser and a coupling coil inductively coupling the Ytrame with the secondary circuit, the center of the coupling coil being connected to the ground and the circuit of the frame being electrically symmetrical With respect to this ground, and a llarsuF ay cage enclosing the Whole oi the receiver circuit, with the exception of the movable self induction and the tuned condenser ot the frame.

2. In a station lor duplex Wireless signalling, in combination, a receiving antenna of the loop type and a sending antenna, said receiving antenna being so arranged as to have its plane inclined to the vertical in such a n'ianner as to etl'ect coincidence between thek said plane and the plane o' rotation oi' the vector representating the magnetic flux emanating from the sending antenna.

In a duplex radio signalling system the combination of a transmitter and a receiving system including a loop aerial in the same locality disposed in a. line substantially perpendicular to the direction ol said trans- `niitter, and means cooperating With said loop for confipensating for any unsymmetrical relations between it and the conductors of the transmitter having oscillations induced therein. f

l. In a duplex radio signalling syst-em the combination of a transmitter and a receiving system includino' a loop aerial in the saine locality disposed in a line substantially perendicular to the direction of said transmitter, and a directional collector coupled to said loop cooperating with said rst mentioned loop for compensating for any unsymmetrical relations between Said loop and the conductors of the transmitter having oscillations induced therein.

5. In a duplex radio signalling system the combination of a transmitter and a receiving system including a loop aerial in the same locality disposed in a line substantially per pendicular to the direction ot said transmitter, said loop aerial having a tuning condenser and a coupling coil symmetrically disposed in series in said loop and means cooperating with said loop for compensating for any unsymmetrical relations between it and the conductors of the transmitter having oscillations induced therein.

G. In a duplex radio signalling system the combination of a transmitter and a receiving system including a loop aerial in the same locality disposed in a line substantially perpendicular to: the direction of said transmitter, said loop aerial having a tuning condenser and a coupling coil symmetrically disposed respectively in the upper and lower.

conductors and in series in said loop, a secondary receiving circuit, a Faraday cage enclosing the secondary circuit and the coil, and a directional auxiliary collector associated With said loop for compensating for any unsymmetrical relations between said loop and the conductors ot the transmitter having oscillations induced therein.

7. In a duplex radio signalling system the combination of a transmitter and a receiving system including a loop aerial disposed in a line substantially perpendicular to the direction of said transmitter, said loop aerial having a tuning condenser and a coupling coil symmetrically disposed in series in said loop, a ground connection to the middle point of said coil, said transmitter having ele-ments disposed substantially symmetrically With respect to said loop, and means cooperating With said loop ior compensating i'or the unsymmetrical relations between said loop and said transmitter. i

8. In a duplex radio signalling system, the combination of a transmitter and a receiving system including a loop aerial disposed in a line substantially perpendicular to the direction of said transmitter, said loop aerial having a tuning condense-r and a coupling coil symmetrically disposed in series in said loop, a ground connection to the middle point of said coil, said transmitter having elements4 disposed substantially symmetrically with respect to the direction of said loop and a second directional aerial coupled to said loop cooperating With said i'irst mentioned loop for compensating for the unsymmetrical relations of said loop and said transmitter elements.

9. In a duplex radio signalling system, the combination of a transmitter and a receiving system including a loop aerial disposed in a line substantially perpendicular to the direction of said transmitter, said loop aerial having a tuning condenser and a coupling coil symmetrically disposed in series in said loop, a ground connection to the middle point ol said coil, said transmitter having elements disposed substantially symmetrical with respect to said loop, and a pair of auxiliary loop aerials at right angles to each other cooperating with said lirst mentioned loop for compensating for the unsymmetrical relations of said loop and said transmitter elements.

l0. In a duplex radio signalling system, the combination of a transmitter and a receiving system including a loop aerial disposed in a line substantialla7 perpendicular to the direction of said transmitter, said loop aerial having a tuning condenser and a coupling coil symmetrically disposed in se- *6 Legault ries in said loop, a' Secondary circuit Coupled to said Coil, a' ground connection to the mid-'- elle point of said coil, Said transmitter haw ing' elements disposed substantially Symmet- 5 rieally with respet to the direction of Said loop, mea-ns cooperating with said loopl for compensating for the unsymmetriealy relation of SeialI loop and said transmitter elements and L Faraday cage enclosing the s'econdary circuit and the aerial coil. 10

In testimony whereof I have signed my naine to this speoilioat'ion.

H Elll! JEAN JOSEPH MARIE d'e REGNAULD de BELLESCZE. 

